Electron emitter



Nov. 2,1948. z. J. ATLEE ELEc'rRoN EMITTER Filed March 3, 1945 PatentedNov. -2, 1948 Zed J. ditlee, Elmhurst, Ill., assignor to GeneralElectric X-Ray Corporation, Chicago, Ill., a

corporation of New York ApplicationMa'rch 3, 1945, Serial No. 580,818

1 Claim. i

The present invention relates in general to electron emission, and hasmore particular reference to the provision of an improved electronemitter, particularly well adapted for use in gaseous conductionelectron flow devices. the invention being concerned specifically withthe use of metallic columbium for electron emission purposes.

An important object of the invention is to use columbium as an electronemitter; a further object being to provide an electrode comprisingcolumbium for operation as an electron emitter in an electron flowdevice; a still further object being to provide an improved electronflow device having an electron emitting cathode comprising columbium.

Another important object is to provide an emission device including anemission element com# prising columbium carried on a suitable mountingcomprising material having a low sputter factor, high melting point andlowelectron emissivity; a further object being to utilize beryllium as amounting for the columbium emitter.

Another important object is to provide an improved gaseous conductionglow lamp having a cathode comprising metallic columbium.

Another object is to provide a gaseous conduction lamp having anelectrode embodying a columbium metal electron emitting elementsupported on a mounting of substantially non-sputtering high meltingpoint material, such as beryl- Another important object is to provide acathodet cimprising a plate or sheet of pure columbium me a Anotherobject is to provide a cathode comprisbodiments of the invention for thepurpose of demonstrating the same.

Referring tothe drawings:

Fig. 1 is a sectional view taken through a glow` discharge lamp devicefitted with electrodes in accordance with the present invention;

Flg. 2 is an enlarged sectional view of a portion of the device shown inFig. 1;

Fig. 6 is a sectional view showing another electrode form; and

Fig. 7 is a sectional view taken substantially` along the line 'l-l inFig. 6. To illustrate the invention, the drawings show electron flowdevices comprising glow dischargel lamps, although the invention. ofcourse, is not necessarily limited to glow lamps, but may have widerapplication wherever electron emission is needed. The discharge deviceseach comprise a sealed envelope Il, preferably of glass andIconveniently fabricated inelongated tubular form. although otherenvelope forms may. of course, be

employed. if desired. The envelope Il may conby passing current throughthe conductive medium between the electrodes.

Any suitable gaseous conduction medium, such as neon, argon, crypton,mercury vapor and other gaseous media, may be employed in the envelopeil. An important diiculty, however, that is encountered inthe operationof gas conduction devices of the character mentioned `is apparentconsumption, evaporation or disappearance of the gaseous medium duringthe operating life of the lamp. It is thought that such disappearance isin reality a deterioration or disintegration or some sort of conversionof the gas by the action of the electrodes thereon in the presence ofthe high heat and electronic activity which prevails in the deviceduring operation, for the material of the electrodes employed appears tohave an eect upon the rate at which the gas is used up or its conductingqualities impaired.

It is the purpose of the present invention to provide improvedelectrodes Il, the use of which in gaseous conduction electron flowdevices will greatly extend the life and improve the performancethereof.

In gaseous conduction devices, the conducting u medium may be ionizedand thus rendered conducting either as a result of the application ofrelatively high potential between electrodes, or by constituting theelectrodes as electron emitting devices.

Where ionization of the gaseous medium is accomplished by electronemission from electrodes separately excited for that purpose, emissionis accomplished, usually, by heating the electrode, and the electrode soheated may conveniently be referred to as a hot cathode. Such a "hot"cathode may be employed in combination with s. spaced electrodecomprising an anode, which need not necessarily be an electron emittingelement, to provide means for delivering electrical current.unidirectionally, through the gaseous medium from the anode to thecathode in order to cause the medium to glow and constitute the deviceas a lamp. A pair of hot cathodes, however, may be employed in order toallow the lamp to be operated by the application of alternatingpotential between the electrodes, in which case the electrodesalternately function as anode and cathode to permit current flow inalternating directions therebetween.

Where the electrodes are not separately excited, as by heating the samefor electron emission, they may be designated as "cold" cathcdes. Indevices embodying cold cathodes, it is necessary. in order to start thedevice in operation, to apply potential, between the electrodes, ofsufficient intensity to cause current flow therebetween, such potentialbeing substantially in excess of that required to initiate current flowbetween hot cathodes. It is, however, advantageous, in a deviceembodying cold cathodes, to fabricate the electrodes of` electronemitting material, since the flow of current therebetween, itself heatsthe electrodes and if the same comprise electron emitting material, suchheating will result in electron emission and facilitate the flow ofcurrent through the gaseous medium after the device has gone intooperation. Where the electrodes comprise electron emitting material,operation of the device can be accomplished more efficiently and atles-s cost than where ordinary non-emitting electrodes are employed.

For the purpose of operating gaseous conduction devices, I propose theuse of pure columbium metal as an electron emitting element inelectrodes. whether the same be constituted as hot or "cold cathodes.

In Figs. 1. 2 and 3 of the drawings I have shown electrodes f3constituting hot cathodes, the same comprising a mounting l5 carrying adisc l1 of pure columbium metal. The disc when heated comprises anelectron emitting element. The mounting I5 provides an annular seat I9in which the emitter disc Il is soldered. brazed r otherwise suitablysecured. The mounting I5 also provides a cavity 2i behind the emissiondisc I1, the rearward surface of which is exposed in the cavity.

The support I is mounted within the envelope in any suitable orconvenient fashion, the same being preferably secured on, andelectrically connected with. metal support rods 23 which are sealinglysecured in and extend outwardly of the envelope. As shown in Figs. 1 and2, these mounting rods 23 extend through pinch seals 25 formed at theopposite ends of the tubular envelope Il. Electrical potential for theoperation of the gas conduction device may be applied I between theelectrodes i3 by connecting the exposed ends oi the support rods 23, atthe opposite ends of the device, to a suitable source of electricalpower.

In order to heat and thus activate the electron emitting elements i'lfor electron emission, I provide, within the cavity 2|, a. suitableheating diament 21, said filament being electrically connected at itsopposite ends with lead conductors 29 mounted in and extending throughthe pinch seal 25. Heating current may be supplied to the filament byconnecting the outwardly extending ends of the conductors 29 with asuitable source of electrical potential.

The mounting l5 preferably comprises material having a high meltingpoint and low sputter factor. The material of the mounting I5 alsopreferably has low electronic emlssivity and I have found beryllium tobe exceedingly well suited for use as a non-sputtering, non-emittingmounting for the electron emission element I1.

In Figs. 4, 5, 6 and 'i I have shown electrodes of the co1d" cathodetype, which are not separately excited for electron emission, but fromwhich electrons are emitted as a result of the application of electricalpotential directly between the electrodes. The electrodes may be of anypreferred shape. As shown in Fig. 4, however, the electrode comprises adiscA 3i of pure columbium metal mounted on support means comprising,preferably beryllium, wires 33 formed at their inner ends to receive andsupport the disc il, which is attached to the wires by soldering,brazing. welding, or other suitable fastening expedient. The wires 33extend outwardly of the envelope through the pinch seal 25 and serve asmeans for applying electrical potential to the electrode disc 3| from a'suitable power source, outwardly of the envelope.

As shown in Figs. 6 and 7 of the drawings, the electrode |'3 comprises aspiral coil or filament 35 of columbium. The filament is preferablyarranged as a pancake coll, secured, at its center, on a suitablesupport 31. This support 31 may comprise va conductor extendingoutwardly of the envelope through the pinch seal 25 and may comprise arod or stem of beryllium to which the coil may be connected in anysuitable fashion, as by soldering, brazing, or welding. The support 31,however, may comprise an integral extension of the material of the coil35. The conductor 31, of course, provides means for connecting theelectrode with a suitable external source of lamp energizing power.

By thus employing electrodes of pure columbium metal havingsubstantially non-sputtering characteristics, I am able to appreciablyimprove Vthe operation of gaseous conduction devices. This improvementis not only in the eiiiciency of operation of the device, but alsoincludes an improvement in the rate of deterioration of the gaseousconduction medium to the end that the operating life of devicesembodying my new electrode is substantially extended.

It is thought that the invention and its attendant advantages will beunderstood from the foregoing description and 'it is obvious thatnumerous changes may be made in the form, construction and arrangementof the several parts without departing from the spirit or scope of theinvention, or sacrificing any of the attendant advantages, the formsherein disclosed being the f' selected embodiments for the purpose ofdemonstrating the invention.

Having thus described the invention, what I claim as new and desire tosecure by United States Letters Patent is:

A gaseous conduction device comprising a sealed envelope of glasscontaining a gas, an electron emitting member comprising columbium, andmeans for supporting said member on and in said envelope comprising a,length of beryllium wire electrically and mechanically secured to saidmember within said envelope, said wire extending outwardly of theenvelope and being sealed to the envelope and thereby supported thereon.

ZED J. ATLEE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Number i Coolidge Jan.,2, 1917 NumberNumber

